服务组合是构建复杂Web软件的有效方法,但服务事务状态的多样性使得服务组合的可靠性难以保证.为此,提出一种构造可靠服务组合的协调方法.该方法采用Petri网对工作流建模,以清晰地表达任务及任务之间的逻辑关系.在此基础上,根据服务的事务属性及服务组合的失效处理机制建立服务组合的失效处理模型,并提出一种构造可靠服务组合的协调策略及实施方法.利用Petri网相关理论证明该策略的有效性.旅游服务实例演示了协调技术的应用方法及其可行性.
Service composition is an effective way to build complex Web software systems. How ever, the diversity of service transaction states makes it hard to guarantee reliability of the composite service. This paper presents a coordination method for constructing reliable service composition. Petri nets are used to modeling workflows, such that tasks and their relationships are articulated. Based on this, a Service Composition's Failure Processing (SCFP) model is established according to transaction properties and service failure processing mechanisms. A coordination strategy and the corresponding enforcement method for constructing reliable service composition are proposed. Theories of Petri nets help prove soundness of the strategy. A case study of Travel Service demonstrates the usage of the coordination technique and its feasibility as well.